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Monday, 17 January 2011

Dimethicone (or polydimethylsiloxane) is one of the main silicones used in hair products. Let me start by clearing a common myth. It does not evaporate. I have included an image showing you some dimethicone fully set as a disc just to emphasize the point.

The type of silicone used in hair is not exactly like that solid though it still does not evaporate. It behaves like an oil and is sometimes referred to as silicone oil.

Here is the dish on dimethicone:

DIMETHICONE (polydimethylsiloxane)

Property

Notes

What is it?

A silicone.

Where is it derived from?

Chemically synthesised

Does it evaporate?

No

Is it water soluble?

No. It can be rubbed off to a very small extent but in general water is not sufficient to clean it off.

Do you have to use a sulphate (SLS) shampoo to clean it off?

SLS containing shampoo is the ideal for good removal. However, other milder sulphate free surfactants can slow or stop silicone build up.

ACTION IN HAIR CONDITIONER

What does silicone do in shampoo and conditioner?

It is added in as a conditioner

How much dimethicone is added?

Varies greatly. 3-5% is around the mark for most rinse out conditioners and shampoos. Leave in conditioners can be in the same range but can equally go as high up as 80-90% for serums.

Is dimethicone a major component of shampoo or hair conditioner

No it is not for shampoo. It varies greatly in conditioner but is generally within (or just outside) the first 5 ingredients after water.

ACTION ON HAIR

Does dimethicone do anything to hair itself

1. It adsorbs (sticks on) on to the outer cuticle of hair.
2. It forms a film on the hair which smoothes down the cuticle
3. It lubricates the hair and is thought to contribute to easier wet combing (i.e less friction).
4.In hair serum, for thermal processing, dimethicone is a heat protectant

Does dimethicone penetrate hair?

It is not known to. It has no charge and tends to form a film outside hair rather than penetrate.

Does dimethicone prevent hair from absorbing water?

In shampoo and rinse out conditioners, it is actually considered a permeable water barrier. Which means it is a barrier to water but it does not fully prevent water entry and exit.

38 comments:

I just bought some cheapie White Rain Tropical coconut (used to add it to my DCs back in the day) and noticed it had Dimethicone in it. This post is right on time. I guess I'll use it as a detangler and shampoo afterwards.

Ms gg - I think the myth has some founding. Some people use styling serums (things like frizz ease) to enhance curls. These thick serums essentially form a really thick coating on hair meaning water is unlikely to get through. Great for heat protecting or anti-humidity though.

However in regular shampoo and rinse out conditioners, the amount of dimethicone added is small therefore it cannot completely obstruct water.

Thank you for posting this information, Jc. I've been wondering about dimethicone for a while. Some have been saying no to cones, but this information right here makes me comfortable about incorporating dimethicone into my regimen. Thanks again!

I must not understand what you mean about water being unlikely to get through thick serums. If you put a thick serum on your hair, let's be extreme and say for 3 days in a row w/o washing, couldn't you still take a spray bottle and dampen your hair with a few sprays? Doesn't that mean water is getting through?

Thank you for these helpful ingredient reviews! It gives some arguments at hand when you are having one of these discussions about Silicones and all. And when reading ingredient lists in the drugstore =D

Little One - Yes hair gets wet as dimethicone is a permeable water barrier. In reality the film formed is never perfect so there is always a way for water to get in.

However dimethicone is the same stuff that is used in bathrooms to prevent water seeping into cracks. Why? In a thick layer it is an excellent barrier for water.

It is not a product that should be layered up, the thicker the layer and the more well spread it is, the less water hair absorbs (which is not bad if you are fighting humidity or wanting to keep a straight style). However if your goal is to keep some water in hair then less is more.

Many people who use silicone serums as a regular styling aid eventually give them up or combine them with something more moisturising like a glycerin gel.

Oh I should clarify too Little One that the silicone serums are intended to fight humidity which causes frizz in looser curls. This is the water (i.e water in air) that the product is supposed to prevent entering the hair.

I agree with everything you said re: dimethicone. However, if you're trying to *maintain* the moisture from your last wash/condition, then I believe it makes sense to use silicones (although dimethicone is not ideal).

If you don't feel like that moisture is at all adequate, then you would be focused on your ability to *add* moisture in between washes. And I guess, add it quickly if you are concerned about silicones slowing absorption.

I read through that article that LittleOne posted, and now I find myself confused lol. It went against a lot of other things I've read. I guess really it is trial and error, and see what works best for your hair.

LaNeshe - I do think it is trial and error always. I personally find that my hair likes a lot things that it shouldn't including silicones!

Personally, I pay very little attention to articles without citations and in my view the article is more of an educated view rather than scientific fact. It is not a bad article but it is not objective (i.e not biased). It appears to be written from the established though inaccurate view that African hair is weak.

Within the first few sentences, I stopped reading and scanned down for references. I didn't see any. I was looking to see if she had actually done a literature search because many of the points in the beginning are actually well researched and to be objective, you have to cite all studies and not just one.

Example

Hair strength - I have talked about the 4 reported studies on hair strength. 2 of which found African hair to be as strong as Caucasian and Asian hair, 2 of which found it to be weaker. There is no conclusive evidence that African hair is weaker, it is disputable scientifically.

I also did not agree with her on breaking strength - I tested my own hair (dry) and found it did not break at 80g, some others reported here too that their hair took much more weight. Caucasian hair can anchor 70-100g according to literature, well in line with African hair.

At this point I stopped reading because the article was not relevant to me (i.e I need need need some citations so I can look them up and expand my knowledge!)

I do not think the advice in it regarding ingredients and why they may be useful is bad, in fact it is pretty good. I just think that the article was biased.

I just wanted to share that in the Frizz Ease serum directions, they advise to work it in on dripping wet hair. A lot of other leave-ins directions say to use them on towel dry hair. After what I've been reading here, I would conclude that the Frizz Ease instructions say so, so that you keep the fresh water inside the hair.

Gerlinde - Yes products like frizzease are best used on hair that has just been washed or wetted. Silicone in styling serums acts to keep in that water but prevent more from getting in (i.e humidity resistance).

Little One - I definitely can compare my test to lab research simply because I repeated it on atleast 10 strands of hair (if not more!). A breaking strength test would do exactly the same, anchor on different weights until the minimum required to break hair is reached. The test would then be repeated atleast 3 more times to be statistically significant. A tensile test is something I cannot do at home though, this would involve recording forces and elasticity and requires specialist equipment.

I think the article was biased only because it reported half the story. The papers which do not follow the same opinion were neglected. I don't think it arises from her being a formulation scientist, I think it probably comes from lack of in depth research (i.e she has not looked at or analysed all the current research on African hair before writing the article).

Hi JC, I am doing a larger study on Dimethicone in skincare. How do you view the down sides? Can it build up on skin as well keeping the skin from doing its main functions? Would you - yourself - use skincare products containing this silicone? Thank a lot.

Much like in hair products, dimethicone being an oil has the potential to prevent moisture going through to the skin. This can be an advantage (e.g setting make up) and a disadvantage (if your skin is very dry). It all depends on how much and what type of dimethicone is used in the product. So there is no definitive yes or no answer, it is a question of trying the product yourself

Hi. I found your site by browsing dimethicone. I am a breast cancer patient (doing quite well generally) who has developed rashes on my arms since treatment. I was given extensive patch testing for allergies to chemicals in products. I came up positive for allergies to dimethylamine (also called amidoamine, dimethylaminopropylamide, lexamine, octadecanoylamidopropyldimethylamine, and other things). Can you tell me if dimethicone is the same thing?I will appreciate any help that you are able to offer.

No they are not the same thing, dimethicone is a pure silicone and has no amine groups.

However there are silicones and dimethicone variants which have amine groups like amodimethicone. Strictly speaking this is not dimethylamine but it has some similarity in chemistry terms due to the presence of the amine group.

I returned the shampoo and conditioner (Dry Remedy 500ml) I bought yesterday and got refund from Aveda Hong Kong. It costs totally HK$ 1,120, still hard to believe their products carry chemical substance – Dimethicone and this substance is not recommended by dermatologist. Thank you very much for your post indeed.

Everything is a chemical in my book. Dimethicone actually is recommended by some dermatologists to help retain moisture. It is very common in skin creams. If there is a reason why you are allergic to it, then that is definitely a reason to avoid it but it does not mean everyone else will dislike it.

I actually started using serums to seal my hair after reading this article a while ago. And it did achieve the second point mentioned which is that it forms a film on the hair strands. I no longer enjoy the greasy hair that comes with oils n butter sealants, so silicones have been a great substitute for me. I love the silky feeling i gives my hair and also the slippery feeling I get when I rub my hand down my hair. My hair also breaks less now because the individual strands don't tangle with each other as it used to due to the slippery nature of each strand. So I guess the "film" really makes my hair feel stronger.

I have to admit that I only use sealant during a shampoo wash week, if its a cowash week, then ill use coconut oil which rubs off quickly.

I really enjoy a spray detangler called Mane and Tail. It lists dimethicone has the second ingredient. I only spray a couple times per section, 8 sections in all. I apply a whipped shea product over that and seal with my oil blend. Is the dimethicone keeping the other products from absorbing? Also, 3 days after my wash day, I like to run water over my head and retwist with the butter, again, is the silicone blocking my hair from absorbing the water and shea butter? Thank you for answering my questions.

PDMS does evaporate, as it's a volatile substance. Some end caps may prevent it from evaporating, but for the most part those are very few. And on that note, PDMS doesn't always refer to the most basic of the substance, as it does require endblocks. For example, a trimethylsiloxy terminated (end blocked) polydimethylsiloxane. And any MSDS sheet will refer to it as straight PDMS, (like GE's Viscasil, which is a trimethylsiloxy terminated PDMS).

It's also a liquid at room temperature. The photo you posted is modified PDMS.

Please do more research into a chemical before blasting away on specs which aren't true.

I would definitely appreciate a reference to your comment as I take references seriously. It would also certainly help if you were polite too, I know it is difficult given that the internet has led people to reduce dialogue but you can change that. This is an open forum for science and I will happily answer genuine scientific queries

1.The PDMS selected for use in rinse out conditioners is deliberately chosen for resistance to wash off. It is non water soluble and non-volatile. High molecular weight PDMS is generally used. Low molecular weight silicones which can evaporate find their use mainly in antipersipirants, but this blog is specifically for hair and hair related science.

2. IF you had read the article you would see that I wrote that the silicone used in hair products is different from that pictured, but the picture was used for illustrative purposes. I also stated that the silicone used in hair products is like an oil.

Hello Jc,recent I purchased schwarzkopf extra care hydro collagen shampoo which has dimethicone in its ingredients list.IJust wanna know that is it ok to use that shampoo on a regular basis like thrice or twice a week and will it harm my scalp or roots??plz reply asap...eagerly waiting for your reply

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